I would have thought the SSH gave it away
If you don't know what it generally stands for w.r.t computers, chances are you don't need it.
But I know people can't resist anything with the word FREE attached ... even if they have no use for it
Secure SHell client for those that are interested, eg. connect to your Linux VPS, etc.
PRO upgrade adds the ability to proxy over the connection, among other things.